The Italian outfit qualified for the knockout stages by virtue of a goalless draw with Ajax in the final round of group games.
Seedort's men sit a disappointing ninth in Serie A after an underwhelming campaign and will go into Wednesday's first leg as underdogs against an Atletico side enjoying a superb season.
Atletico reached the last 16 by topping Group G with an unbeaten record, conceding only three goals in the process.
Diego Simeone's side are level on points with Barcelona and Real Madrid in an absorbing La Liga title race, but despite the two teams' contrasting fortunes this campaign, Seedorf is confident Milan can come out on top at San Siro.
"The team is ready and motivated," Seedorf said. "We are going to face a team that is doing well. We are really motivated. It will be a great night, full of chances to reap the benefits of our hard work.
"The Champions League is a special moment, it is a very important competition and we are happy to represent Italy. I am satisfied of what everybody did this week to be at their best.
"Atletico deserve respect. They are a strong team, well organised, but they have chinks that we hope to exploit.
"We will give our best and we will hold together. We are on the eve of an important game, but we live with balanced and intense feelings.
"In terms of our attitude, we are on the right track and of course we must continue to improve with humility. I see the guys and they are very determined."
